A switched telephone network typically includes one or more switching offices that serve subscriber loops of subscriber terminals (e.g., telephones). Such a switching office is referred to as an "end office" and contains as its major equipment component a local exchange switch (e.g., a "class 5" switch). This switch terminates the facilities that connect subscribers to the network. The local exchange switch also terminates interoffice trunk facilities ("trunks") that carry calls through the network to subscribers served by other switching offices. The main function of the switch is to establish interconnects between pairs of subscriber loops connected to the switch or between subscriber loops and trunks, depending upon whether or not both subscribers in a call are served by the same end office switch.
The invention provides methods and apparatus implementing a technique for a "virtual" end office. The virtual end office includes one or more pre-switch adjuncts forming a single logical construct. Each pre-switch adjunct is connected to a local exchange switch in a telephone network and provides special services to subscribers, such as high speed Internet access or "video on demand". The pre-switch adjuncts have a common exchange prefix code and so a subscriber can access special services from anywhere in the network by using the same exchange prefix code, so long as the switch the subscriber is using is connected to a pre-switch adjunct. This common access forms the virtual end office.
In general, in one aspect, the technique includes receiving a subscriber request for special services from a subscriber at a subscriber terminal, where the subscriber request includes an exchange prefix code indicating the virtual end office; transmitting the subscriber request to a local exchange switch connected to the subscriber terminal; transmitting the subscriber request to a pre-switch adjunct which is assigned the exchange prefix code of the virtual end office, where the pre-switch adjunct is connected to the local exchange switch and to the subscriber terminal; and providing special services to the subscriber terminal from the pre-switch adjunct.
Advantages of the technique includes one or more of the following: the special services are implemented by equipment (i.e., the pre-switch adjunct) installed such that the equipment interfaces both to the facilities that connect the subscriber to the switch (i.e., the subscriber's line) and to the switch; the pre-switch adjunct permits normal use of the subscriber's line to receive calls and when dialing numbers that do not access the special services (i.e., voice calls); logging of a call requesting special services can be implemented by the switch, for billing or other purposes; examination of the dialed number is based upon existing network capabilities, such as centrally defined toll-free numbers; recognition during the call that the subscriber's line is engaged, enabling a busy signal to be returned to callers attempting to dial the subscriber from elsewhere in the network; correct functioning of enhanced services associated with the subscriber, including but not limited to call forwarding and voice mail; the traffic on the telephone network is reduced by diverting special service calls at the pre-switch adjunct; special services which cannot be provided over the telephone network are made available through a direct connection between the subscriber terminal and the pre-switch adjunct; and all of the above can be obtained without modification to the functional implementation of the local exchange switch (notably, its stored program control software).
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.